The ability of a diagnostic test to correctly identify individuals who have the disease is called:

Sensitivity (true positive rate) = TP / (TP + FN) — the proportion of people WITH the disease who test positive. A highly sensitive test has few false negatives; if negative, it rules out disease ('Sn-out': Sensitive test Negative rules OUT disease). Specificity (true negative rate) = TN / (TN + FP) — the proportion of people WITHOUT the disease who test negative. A highly specific test has few false positives; if positive, it rules in disease ('Sp-in'). Positive predictive value = TP / (TP + FP) — probability that a positive test result is a true positive. Negative predictive value = TN / (TN + FN) — probability that a negative result is a true negative.